Turning off sub-sonic filter when measuring cartridge-arm resonance

（中文在後）
Some USB sound boxes/cards, preamps, and phono stages have subsonic filters to suppress ultra low frequency noise from playing record warps, etc. When measuring the natural resonance of a cartridge-tonearm combo, be sure to turn the feature off, otherwise one may get incorrect readings. Figure 1 is with the filter turned ON in the ART USB Phono Plus while Figure 2 is OFF and shows better results.

有些USB音效盒，前級與唱放有超低頻衰減功能，播放不平的唱片時可保護喇叭或其它器材。但在測量低頻共振點時（Adjust+ 裡的 f res功能），要將這功能關閉，才不會影響結果。圖1是ART音效盒的濾波ON，圖2是OFF。後者明顯得到比較符合預期的結果。